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L.A. Dolphin Project 3

 

L.A. DOLPHIN PROJECT 3




RISSO'S DOLPHIN ECOLOGY

 

 

The Santa Monica Bay, located within the Southern California Bight, is home to a variety of marine mammal species. Risso's dolphins (Grampus griseus) were rarely observed in this area prior to the El Niño event in 1982-1983, and a change in Risso's dolphin occurrence in the bay was observed after the 1997-1998 El Niño event. The occurrence and behavior of this species in this study area and nearby locations have never been examined. This study aims to provide new data on Risso's dolphin occurrence, aggregations with other species, frequency and behavior for the study area, including inside and outside the boundaries of the new Marine Protected Areas.


Data Collection Techniques

Boat surveys are conducted in the study area, on an average of three surveys per month. Data on Risso's dolphin schools are collected at 5-min intervals using the software LOGGER and include: number of individuals, size classes, behavior, and aggregations with other cetacean species. These animals are photo-identified for this study and further comparisons with other scientists.

inshore bottlenose dolphins
Bottlenose dolphins were found in aggregations with Risso's


Project Objectives

The main objectives of this study on Risso's dolphins aim to determine:

  • Distribution, occurrence and sighting frequency
  • School group size
  • Behavioral patterns
  • Aggregation between Risso's dolphins and other marine mammal species
The data collected during this study will also allow for data comparison between Risso's dolphins found in California and other populations of this species around the world (e.g., Mediterranean sea).

Conservation and Management Implications

Data are needed on occurrence, distribution, movements, population dynamics and trends in Risso's dolphin populations in California, and better information on the threats (e.g. bycatch in fishing gear) facing these animals is needed to inform future conservation & management efforts.

Sea surface tempertaure charts  

Satellite charts show sea surface temperatures (NOAA)
Sea surface temperature images
© 2005 CoastWatch


 

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